Pallets and grate bar therefor



P 1956 w. M. DUNCAN PALLETS AND GRATE BAR THEREFOR 2 Sheets-Sheet 1Filed 001.. 21, 1954 M N R a mu N 8 v M "W 5: 7 u 3 M \5 W W b .3 Y B 9)5 3 A TTORNEYS Sept. 25, 1956 w. M. DUNCAN 2,764,403

PALLETS AND GRATE BAR THEREFOR Filed Oct. 21, 1954 2 Sheets-Sheet 2 FIG.3.

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V F W 37 35 I27 INVENTOR, WILLIAM M. DUNCAN w meegflww ATTORNEYS UnitedStates Patent This invention relates to the pallets of a sinteringmachine or related apparatus, and more particularly to the constructionand attachment of the grate bars of such pallets.

It will be understood that in the heat treatment of ore and othermaterial, it is customary to utilize a machine having a series ofpallets entrained upon an endless track. The material to be sintered orotherwise treated is fed onto the pallets as they move from one end ofthe machine and is heated as the pallets move toward the other end,where the material is automatically dumped. Each pallet has a grate-likebottom formed by elongated grate bars seated at their ends on a pair oftransverse frame members, which bridge the space between the sides ofthe pallet. Since the grate bars deteriorate in use, they are usuallyreplaceable. Accordingly, it has been customary to form grooves alongthe transverse frame members, the grate bars being individually insertedtherein or withdrawn therefrom from one side of a pallet.

This type of pallet is not entirely satisfactory, however, because theretaining grooves become clogged and the grate bars warp, with theresult that difficulty is experienced in sliding the bars within thegrooves. Also, it is not uncommon to find that it is necessary to removenearly all of the bars in order to replace only a few defective ones. Itis therefor an object of this invention to provide an improvedarrangement for securing the grate bars on a pallet, and especially, toprovide for individual replacement of selected bars withoutdisarrangement of the others.

In addition, it is to be observed that these pallets typically are fromsix to twelve feet in width and two feet in length. The grate barsaccordingly are two feet long and perhaps an inch wide, and as such aresubject to warpping. The elongation under heat is not particularlytroublesome, but the lateral deflection of the bars gives rise tooperating difliculties. One of the objects of this invention, therefore,is to provide a pallet wherein such deflection or curling of the gratebars is substantially eliminated, or at least, is so slight as not tointerfere with the operation of the machine or the attaching means forthe grate bars.

Briefly, these objectives are achieved by forming the grate bars withdepending ears, each ear being shaped to embrace a holding rod thatextends transversely beneath the bars between the sides of the pallet.Preferably, the holding rods are of non-circular cross section, and thedepending portions of the grate bars are formed with upwardly extendingslots of key-hole shape. The narrow base of each slot is of a widthslightly greater than the narrow dimension and less than the widedimension of a holding rod. With this arrangement, any grate bar may bereadily removed or inserted, upon rotation of the holding rod so thatthe thin section thereof is aligned with a narrow part of the key-holeslot. The grate bars are simultaneously locked in position by rotatingthe rod to a position such that the thick section thereof lies acrossthe narrow base of the several slots,

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the rod then being secured against rotation, as by clamps affixed to thepallet at its sides.

In order to minimize heat-produced deflection of the grate bars, thepallet is formed with at least three, and preferably four transverseframe members in spaced relationship from one another. The grate bars,then are of a reduced length, such as to bridge only two of thetransverse frame members.

Other features of the invention will be in part apparent from and inpart pointed out in the following detail description taken in connectionwith the accompanying drawings, in which:

Fig. 1 is a transverse section taken on the line 1-1 of Fig. 2, showinga pallet embodying features of this invention;

Fig. 2 is a section taken on the line 2-2 of Fig. 1;

Fig. 3 is a section taken on the line 33 of Fig. l; and

Fig. 4 is a sectional View similar to that of Fig. 2 but illustrating analternative embodiment of the invention.

Referring now to the drawings, there is shown a pallet having the usualside walls 1 and an open frame formed by members 3 and 5. The frameportions 5 define the sides of the pallet, whereas the transverse framemembers 3 bridge the space between the sides at the ends of the pallet.These transverse members 3 may be reinforced by a web 7 extendingtherebetween intermediate the sides of the pallet, and there may beadditional transverse frame members 9 extending parallel to and betweenthe end-forming members 3. Rollers 11 are journalled on the sides 5 ofthe pallet for cooperation with track-forming rails 13, although thetrack could be formed of rollers on which the sides 5 of the palletwould ride.

It will be understood that sprockets are generally provided at theforward end of the machine to lift the pallets from a lower reach oftrack to an upper track where they are loaded with the material to beheated and admixed fuel. The pallets are moved along the upper track inabutting relationship with one another, so as to form a continuoustrough, a draft being induced through wind boxes beneath the pallets tocontrol burning of the fuel. When pallets individually reach the end ofthe upper track, they roll down a reverse bend, thereby dumping theircontents, and along the lower reach of track to collect adjacent thesprockets. Such a machine is shown, for example, in my Patent No.2,519,179.

In accordance with previous practice, the frame elements 3 extendingacross the pallet were formed with grooves in which the grate bars wereseated. These retaining grooves, in turn, had slots at their ends or atone side of the pallet so that the grate bars could be individuallywithdrawn and inserted therein; but it will be apparent that thispractice is somewhat slow and diflicult. Although only a few of the barsmight need replacement, it was generally necessary to remove aconsiderable number of other bars before the defective ones could bemoved to the slots at the side of the pallet. Furthermore, warping ofthe grate bars and clogging of the retaining grooves interferedseriously with the replacement of the grate bars.

These difliculties are herein avoided by securing the grate barsindependently of the transverse frame members. In particular, the palletcarries a plurality of standard grate bars 15, a pair of side bars 17and certain center bars 19. Each of these grate bars is formed with anelongate body which bridges and rests upon the transverse frame members3 and 9, and which may have side bosses 23, the lateral spacing thusachieved providing the draft passages in the grate or bottom of thepallet. The grate bars are then secured against displacement from thepallet by means of a holding rod 25, which extends transversely beneaththe grate bars between the frame members 9 through an opening 26 in theWeb 7.

3 This rod 25 in turn is secured at its ends to the sides 5 of thepallet, and each grate bar has a cooperating part depending from thebody in embracing relationship with the holding rod.

Each of the so-called standard bars has an ear 27 depending from itselongate body 21 at a point between the frame members 9, which ear maybe of a width equal to that of the body. The center bars 19 have arelatively wider body 31 so that the associated ears 29 may be offset toone side, thereby permitting the body portions 31 to overlap the centerweb 7. These ears 27 and 29, in turn, are formed with slots 33 ofkey-hole outline, the mouth 35 of a slot being narrower than thegenerally circular inner head portion 37.

The key-hole slot 33 is designed for use with a holding rod of suchnon-circular cross-sectional shape as to clear the mouth of the slotwhen in one position and to lock over the mouth of the slot when theholding rod is rotated within the head 37 to a second position. Forexample, the holding rod may be a length of square stock, which isreadily rotated by a conventional wrench, and which may be lockedagainst rotation, as by a clamp 39.

Referring to Figs. 1 and 3, the body 41 of a side grate 17 is cut awayat 43 to accommodate the clamp 39 opposite the holding rod. A part 45 ofthe clamp is secured within the recess 43 by the head 47 of a bolt (thebolt having an outer nut 49), so that a leg 51 projects downwardlythrough the grate bar 17. The end of the leg 51 is notched at 53, asshown in Fig. 3, for locking cooperation with the end of the holdingrod, which is otherwise held within a loop-forming section 55 dependingfrom the body 41 of the grate bar.

When the clamp 39 is secured in position, the holding rod 25 is securedagainst rotation in locking relationship with respect to the key-holeslots 33 in the other grate bars 15 and 19. Upon removal of the clamp47, the holding rod 25 may be rotated to a position such that the narrowdimension thereof is aligned with the narrow mouth 35 of the key-holeslot, and any of the grate bars 15 and 19 may be readily lifted from thepallet without displacement of the others. The holding rod 25 is held atits ends by the side bars 17 and by the web 7, so that it does not dropfrom the pallet when rotated to its unlocking position. The rod may beremoved, however, by lifting all of the grate bars, including the twoside bars 17.

In Figs. 1-3, the grate bars are shown to extend the full length of thepallet, which is normally two feet, this being a conventional practice.Grate bars of such length sometimes curl under heat, however, and forthat reason, the invention also contemplates a construction of the typedisclosed in Fig. 4. It has been found that the tendency to curl isgreatly reduced, if not prevented, by reducing the length of the bars,so that a given bar bridges only two of the transverse frame members 3and 9. In that event, each bar is provided with a locking ear 127 forcooperation with holding rods 125. The body portions 121 of the bars arein substantial abutting relationship at their ends 157, the constructionotherwise being the same as that described previously.

From the foregoing description, it is apparent that those skilled in theart will understand the structure, function and mode of operation of theinvention herein disclosed, and appreciate the advantages thereof.Although several embodiments have been disclosed in detail, it is to beunderstood that the invention is not limited thereto, but the drawingsand description thereof are to be understood as being merelyillustrative. It is realized that many modifications and variations willpresent themselves to those skilled in the art without departing fromthe spirit of this invention or the scope thereof as set forth in theappended claim.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:

In a pallet of the type described having sides, trans- 'verse frameelements extending between said sides, and a plurality of grate barssupported on said transverse frame members; the improvement comprising aholding rod extending transversely beneath said grate bars, said holdingrod being releasably secured to said pallet and being of non-circularcross section, each of said grate bars being formed with anupwardly-extending slot of key-hole outline, the narrow mouth :of whichis sufiicient to clear the holding rod in one position and to lock withthe holding rod when the rod is rotated to a second position within therelatively wide head portion of the keyhole slot, a clamp secured at theside of said pallet for locking said holding rod against rotation whenin its position of interlocking relationship with respect to thekey-hole slots of the several grate bars, one of the sidemost grate barsbeing recessed to accommodate said clamp, and said clamp having a legprojecting through Hegeler et a1 Nov. 22, 1932 Clawson May 23, 1933

